1. Field of the Invention
The present invention relates to a die used with a resin-pellet manufacturing apparatus for manufacturing synthetic resin pellets, and more particularly to a die for manufacturing resin pellets provided with a heating means for heating a nozzle portion for extrusion of resins efficiently.
2. Description of the Prior Art
In the die used for the apparatus for manufacturing resin pellets of this kind, a heat channel for causing a heat medium to flow to heat the neighborhood of the nozzle is provided in a die plate in order to prevent the nozzle portion from being blocked up due to solidification of resins because the die surface is cooled by water. The typical prior art relating to the heat channel is disclosed in Japanese Patent Application Laid-Open No. Hei 1 (1989)-278312 Publication. The shape of a heat channel in the die plate is shown in FIG. 12.
Mostly, in the conventional die, a heat channels 21 is provided between adjacent nozzles 22, as shown in FIG. 12, and a sectional shape at right angles to the axis of the channel is a circular round hole. In such a round-hole shape, a heat transfer area is small relative to the opposed nozzles 22. Accordingly, if an attempt is made to improve the heating efficiency, the diameter of the round hole need be made large. Incidentally, in the case of the round-hole shape, drill processing is employed, and oblique processing is possible unlike discharge processing which is carried out in the case of the heat channel having a complicated sectional shape, because of which a channel 23 and a channel 24 on the introducing and discharging sides, respectively, of the heat medium with respect to the heat channel 21 can be processed by bending them obliquely as shown in FIG. 13. Accordingly, the heat channel 21 is made closer to the cooling water side (the left end side in FIG. 13) to enable minimizing the effect of water cooling.
However, in the heat channel 21 having a large-diameter round hole shape, the number of nozzle orifices through which resins flow becomes lessened, because of which a method is employed to branch it at the extreme end as shown in FIG. 12. However, the processing of the oblique nozzle orifices is so complicated that much time is taken, resulting in the rise of cost of the die plate.
Separately from the above-described prior art, another example of typical prior art is disclosed in U.S. Pat. No. 4,752,196 Specification, a sectional view of the main parts of which is shown in FIG. 14. In this figure, reference numeral 22 designates a nozzle through which resin flows, and reference numeral 34 designates a heat channel, a sectional shape of which is a triangular shape corresponding to a large diameter and a small diameter of nozzles opposed to each other.
It is necessary for the processing such a complicated shaped heat channel 34 to carry it out over a long period of time using a electric discharge machine, resulting in posing a problem that brings forth high cost of a die plate and a longer period of delivery of products.
The present invention has been accomplished in order to overcome such problems as noted above with respect to prior art. An object of the present invention is to provide a die for manufacturing resin pellets capable of easily carrying out-processing of a die plate, of simplifying the construction of a heat channel, and of enhancing the heating efficiency.
For achieving the above-described object, the present invention provides the constructions mentioned below:
According to the present invention, there is provided a die for manufacturing resin pellets, comprising a row of heat channels comprising a plurality of nozzles forming resin channels and extending through a die to form nozzle orifices in the surface on a die water cooling surface side, and a plurality of heat channels, the row of heat channels being provided between said nozzles, and in the row of heat channels, the heat channels being arranged so as to be adjacent to and along the nozzles. Here, the heat channels can be extended in linear shape substantially parallel to the die water cooling surface side.
According to the present invention as described, there can be suitably used for a die provided with heat channels of a pelletizer of the under-water type or the ring water and hot cut type for manufacturing resin pellets. The provision of rows of a plurality of heat channels increases a heat transfer area and an improvement of heating efficiency.
Further, the die for manufacturing resin pellets according to the present invention comprises a heat medium introducing passage for forming a channel for guiding a heat medium into a die, and a heat medium discharging passage for forming a cannel for guiding the heat medium outside the die, the heat medium passage capable of being constructed so as to connect the heat medium introducing passage with the heat medium discharging passage. Further, there comprises a nozzle part ring formed with a nozzle, an outer die part provided on the outer peripheral side of the nozzle part ring, and an inner die part provided on the inner peripheral side of the nozzle part ring, an outer annular passage capable of being constructed between the outer die part and the nozzle part ring so that an inner annular page is formed between the inner die part and the nozzle part ring. Here, at least a part of at least one of the outer annular passage and the inner annular passage can be used as a heat medium introducing passage, and a part except the heat medium introducing passage can be used as a heat medium discharging passage. Alternatively, the outer annular passage may be divided into two passages in a circumferential direction so that one and the other may be used as a heat medium introducing passage and a heat medium discharging passage, respectively. Otherwise, one out of the outer annular passage and the inner annular passage may be used as a heat medium introducing passage, and the other may be used as a heat medium discharging passage. Further, preferably, in the row of heat channels, the heat channel closest to the die water cooling surface is provided at a position projected on the die water cooling surface with respect to the outer annular passage and the inner annular passage.
Further, alternatively, in the die for manufacturing resin pellets according to the present invention, at least one of the heat medium introducing passage and the heat medium discharging passage may be provided independently for each heat channel in the row of heat channels.
According to the present invention as described, since the flow rates of heat media in the plurality of rows of heat channels can be respectively adjusted according to the heat loads, a supply of heat to the heat channels is carried out in a well-balanced manner of heat by means of increasing the flow rate of the heat channel on the cooling water side or the like to thereby enable provision of a die with high heat efficiency.
Further, in the die for manufacturing resin pellets according to the present invention, the sectional shape of the heat channel at right angles to the axis of flow channel can be made circular. Here, preferably, the heat channel is provided so as to extend in the direction parallel with the surface on the die water cooling side.
According to the present invention as described, since the plurality of rows of heat channels can be formed by a drill processing to enable an oblique hole processing, whereby the heat channels can be made closer to the cooling water side, thus obtaining a die with high heat efficiency.
Further, in the die for manufacturing resin pellets according to the present invention, alternatively, in the row of heat channels, sectional areas of the heat channels at right angles to the axis of flow channel may vary. Here, preferably, the section of the heat channel at right angles to the axis of flow channel are made circular, and in the row of heat channels, the diameters of the heat channels vary, whereby the larger the sectional area of the nearby nozzle at the right angles to the axis of flow channel, the sectional area of the heat channel is made small.
According to the present invention as described, since the diameter of the channel can be changed adjusting to the arrangement of the nozzles, processing of an oblique nozzle orifice need not be carried out adjusting to the heat channel to enable provision of a high efficiency die at less cost.
Further, in the die for manufacturing resin pellets according to the present invention, alternatively, the ends of a part out of a plurality of heat channels constituting a row of heat channels may be closed to provide a heat insulating space. Here, preferably, the ends of the heat channel closest to the die water cooling surface is closed to provide a heat insulating space.
According to the present invention as described, in the case where the conditions of the heat medium as a utility is restricted, for example, in the case where the heat medium merely obtains a steam whose vapor pressure is low, and in the case where the steam cooled by being taken in heat on the cooling water side is condensed into drain to worsen the heating efficiency, and the heat medium merely obtains a relatively low temperature hot oil, the viscosity of oil cooled by being taken in heat on the cooling water side to thereby make it difficult to flow thus worsening the heating efficiency, whereas such a problem can be avoided under the simple construction.
Additional specific objects and advantages, residing in the details of construction and operation, will become apparent as the invention is more fully hereinafter described and claims.